What size tyres fit on this rim: ETRTO 622-18?

I have a Boardman Cyclocross, with Ritchey Disc OCR rims. Theres a sticker on the rims that reads ETRTO 622-18. I've currently got 700x32 Continental CityRide tyres on it, but I'd like to fit some thinner road tyres on it.

However, despite searching on the net, the ETRTO stuff just has me massively confused. There also seem to be disagreement with different sites about what will fit on what.

Does the 18 in the ETRTO number mean the thinner width I can go for is 18" or is this a faux pas and is my actual minimum wide some way higher?

Well I did say 23mm would fit not that they'd be comfortable (I'm not sure safety's an issue, it's the likelihood of getting pinches and damaging the rim rather than blowing off which you get with wide tyres on a narrow rim) as you'd need to pump them up hard - hence

Well I did say 23mm would fit not that they'd be comfortable (I'm not sure safety's an issue, it's the likelihood of getting pinches and damaging the rim rather than blowing off which you get with wide tyres on a narrow rim) as you'd need to pump them up hard - hence

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I think Sheldon does admit some where that his table does err on the side of caution but surely the safety of not having your teeth shake out on 23mm is important

If it looks right it usually is right, you can often see when a tyre is simply too slim for that width of rim to safely resist pinch punctures like Fiona describes.

Don't get hung up on ETRTO - go into a shop and start quoting ETRTO numbers and they will look at you like you are a complete anorak.

With a crosser I would keep it around the 25mm mark as the rims are just that bit broader than a comparable road wheelset, 23mm will run but you are risking dented rims if you strike raised iron work in the road. The old 27"X1"1/14 tyre was used for ages for all sorts of riding in britain because it was a good compromise between speed and durabilty so you should have no problems with a modern 25mm tyre or upwards.

it is very very important you know whether it's inside 18mm or outside 18mm. guessing' no good. and just because the bike came (if it did?) with 32mm means it's right. my fixie rims will fit 35mm spikes, but the max i should have on after measuring is 28mm, could have been nasty. it also explains why my marathon+'s blew off the rims whilst sat in the garage.

The bike came with larger tyres still - obviouly cylocross ones - I believe, but would have to double check they were 35's, Ritchey Excavaders. My long term plan (think a year plus) is to have a road-bike for the dry days, and a cyclocross for the wet days, but in the meantime I've gone for a cyclocross, but with slicker tyres, not knobblies as the best (or worst!) of both worlds. I bought the CityRide 32’s simply because they were what was in the store at the time, but I think I could go thinner until, I get a road bike.

That said, coming up to the winter months its probably more sensible to leave the 32's on... however I've convinced myself to bang the thinnest tyres I can n the cyclocross, and hop back on my old mountain bike if the weather is really, really bad.

Many thanks for all the advice. I think I'll probaly end up playing safe and going for the 25mm. Everyone agrees they'll fit safely, and they will certainly be a decent amount thinner than my 32's anyway.

I agree, although the 23's will fit, the 25's would be more reliable on our roads, as well as more comfortable for the same speed. I can't tell the difference between my last 25's and current 23's in average speeds anyway, but the 25's were definitely slightly more comfortable with some of the local moon surface roads. Better to play it safe.

I think HED and Zipp would disagree with the comments about using 23mm tyres on these rims - their latest rims are 19mm ETRTO and ride very nicely. I wouldn't put anything less than a 22mm Conti Attack on them though.